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TECH TRAK Easier-to-digest ‘meatballs’ for finicky mini-mill melters

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Meatballs go well with spaghetti or smothered with tomato sauce on a long Italian roll. They don't digest well in a steel mill's electric furnace, at least those served up with portions of shredded scrap.

The "meatballs" are copper armatures or parts of copper motors from automotive starters and alternators or the compressor motors in appliances. They are part of the shredded flow because most have a magnetic steel rod.

"The meatballs are still with the shredded because they have a steel shaft in the middle of the copper windings," explained Bobby Triesch, vice president of ferrous operations at Newell Recycling of Atlanta Inc. "Because that steel shaft is there, it jumps over to the magnet."

When a junked vehicle or appliance is shredded, the shredder's magnet picks up that steel shaft and with it comes the copper that some steel mills dread because it can harden their steel products, particularly flat-rolled sheet. That can make it difficult to form into parts like car hoods and doors. To counter that, most shredders have a picking line as the last pass before the shredded is dumped into a pile to be shipped to steel mills or loaded onto a boat for export.

Picking lines are manned by workers whose task is to spot the reddish color of the copper meatballs—hence the nickname—and remove them from the conveyor belt.

Copper wiring doesn't normally make it that far through the shredding process, unless it is bolted to a piece of steel or iron as a grounding wire. It normally drops into the nonmagnetic fluff, or shredder residue. Inshredders with additional downstream separation systems, it often is recovered and sold as nonferrous scrap under such ISRI specifications as Zorba or Zebra. Not to be outdone, the copper-laden meatballs, or shredder pickings, have their own ISRI spec Shelmo.

To reassure steelmakers that they are serving up shredded that is as close to meatball-less as possible, some scrap processors have purchased and installed the Crossbelt Metal Analyzer from Cincinnati-based Gamma Tech LLC. And some flat-rolled mini-mills that want lower copper content in their shredded scrap—as low as 0.2 percent or less—are willing to pay a premium for the so-called Gamma shred.

The Crossbelt Metal Analyzer uses prompt gamma neutron activation analysis technology to identify unwanted metals. It can provide a real-time analysis detailing percentages of metals in the shredded material as it moves along the conveyor, according to metallurgist Daniel Pflaum, president of Gamma Tech. The device's aperture is 20 inches by 70 inches, allowing it to scan the width of the shredder's conveyor belt.

Pflaum said the device does not just spot the obvious chunks of copper, like meatballs—it also analyzes each piece of metal that flows past and determines its copper content as an alloy of the metal.

"We are actually bombarding the scrap with highly penetrating neutrons and looking not only at the free copper content but also the core copper content and the alloy copper content in the base metal," he said.

So the Gamma Tech analyzer can size up pieces of rebar that have been shredded as well as car parts. But the Gamma Tech device doesn't pull the meatballs off the belt. Instead, it enables the shredder operator to adjust the mix of feedstock by, say, using more sheet scrap that contains less copper or any of the other variables in the shredder operations that can alter its output.

Thus far, said Pflaum, there are 13 Gamma Tech analyzers operating at shredders in the United States and two in Europe. River Metals Recycling in Newport, Ky., was one of the first yards to use the Gamma Tech system. Others, like Metal Management Inc., have added them to shredding operations in Chicago and elsewhere.

Much of the pressure to reduce the copper comes from the flat-rolled steel mills. "The solution is in the dilution," said Pflaum. The mills can dilute the melt mix with higher-quality scrap or other materials that contain less copper.

All of the flat-rolled mills have different specifications, he said, but all are below 0.2 percent on copper, with some simply wanting it as low as possible.

Pflaum argues that it does not make much sense for steelmakers to be so obsessed with the 0.20-percent specification for copper in shredded. Instead, he said, they can use shredded with 0.22-, 0.23- or 0.24-percent copper and, knowing that it is there, design the furnace charge specific to that chemistry.

The steel world has become comfortable buying scrap based on its physical description, he explained, and implying from that some sort of metallurgical properties. Now, however, it can know the actual metallurgical properties of the scrap because a system like Gamma Tech's analyzer will give it to them, he said. "What it allows the steel industry to do is dial that grade of scrap up and down to fit the specific needs of the mill without paying for scrap based on its physical description."

In the past month, Fort Wayne, Ind.-based OmniSource Corp. and Innov-X Systems Inc., Woburn, Mass., have agreed to work to develop an X-ray fluorescence system that will both identify the copper and automatically remove it from the conveyor belt.

The first automated copper extraction system will be built for the shredder at OmniSource's home office yard in Fort Wayne, Ind. It is expected to be up and running within two to three months, according to Rick Comtois, president of Austin Automation & Instrumentation, an Austin, Texas, company that works with Innov-X to design such systems.

X-ray fluorescence technology will identify scrap based on the metal's chemistry. But the system at OmniSource is expected to go a step further by removing free and commingled copper, eliminating the need for hand pickers on the line.

Innov-X said that its system will be designed to maximize cost-effectiveness, reducing the copper content in shredded scrap, typically to less than 0.17 percent, diminishing manual picking and obtaining higher-value copper.

Pflaum said OmniSource has asked his company to supply a Gamma Tech analyzer that will be installed beyond the Innov-X system to determine the copper composition of the shredded after it has passed through the automated removal system.

Innov-X and OmniSource are not alone in their plans to pluck meatballs from the shredded stream. Wendt Corp., the Tonawanda, N.Y.-based shredder and eddy current equipment supplier, has its eyes on those copper-steel clumps as well.

William D. Close, a Wendt sales engineer, said the company's German partner, CommoDaS GmbH, will have a production-scale sorting machine available in the second half of 2008 that will use both X-ray fluorescence as well as optical sensors to identify the meatballs and remove them from the shredded stream.

Close said that CommoDaS is involved in the mining industry and has systems that separate large boulders—white rock from black rock—before crushing operations, so it already has experience separating large, heavy objects. Its shredded sorter will be an air separation system, but will be different from anything that has been seen in the metals industry. "We're using elevation drop," he said. "If you visualize an asteroid in space, it does not take much of a nudge to move the trajectory. It's kind of what they are doing, but in a drop configuration. We're not lifting; we're just kind of giving a little help (to move it off the conveyor)."

If the CommoDaS shredded sorter is anything like its mining equipment, it will pack quite a punch. "The air valves on it are so large that it is like a miniature shotgun blast going off," Close said.

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